Flame-retardant wire and cable

ABSTRACT

An electrical conductor or cable, capable of maintaining electrical integrity when exposed to open flame temperatures of 1000* F. without propagating a fire or resulting in falling burning particles or generating large volumes of smoke. The conductor or cable of this invention is comprised of a metallic conductor or plurality of conductors covered by a layer of primary insulation. Such conductors are then covered by a layer of silicone rubber which is, in turn, covered by a layer of glass fiber. The layer of glass fiber may then be covered by another layer of silicone rubber which is, in turn, covered by a layer of braided asbestos impregnated with an intumescent material. In the alternative, the second layer of silicone rubber may be covered by an asbestos tape which is then covered by a layer of elastomeric material having fire-retardant properties.

United States Patent [72] Inventors John G. Stone North Haven; George S.Buettner; Christian A. Alm, Cheshire, Conn. [21 Appl. No. 780,644 [22]Filed Dec. 3, 1968 [45] Patented May 4, 1971 [73] Assignee CerroCorporation New York, N.Y.

[54] FLAME-RETARDANT WIRE AND CABLE 19 Claims, 4 Drawing Figs.

[52] US. Cl 174/113, 117/218, 174/121 [51] Int. Cl 1101b 7/28 [50]FieldoiSearch l74/ll0.7, 113-1 16, 121, 121.1, 121.4; 117/218 [56]References Cited UNITED STATES PATENTS 2,349,951 5/1944 Fullerl74/l21(.4)

Primary ExaminerE. A. Goldberg Attorney-Delio and Montgomery ABSTRACT:An electrical conductor or cable, capable of maintaining electricalintegrity when exposed to open flame temperatures of 1000 F. withoutpropagating a fire or resulting in falling burning particles orgenerating large volumes of smoke. The conductor or cable of thisinvention is comprised of a metallic conductor or plurality ofconductors covered by a layer of primary insulation. Such conductors arethen covered by a layer of silicone rubber which is, in turn, covered bya layer of glass fiber. The layer of glass fiber may then be covered byanother layer of silicone rubber which is, in turn, covered by a layerof braided asbestos impregnated with an intumescent material. In thealternative, the second layer of silicone rubber may be covered by anasbestos tape which is then covered by a layer of elastomeric materialhaving fire-retardant properties.

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INVENT OR John 6. Shane Georqe E5. Bue-Hmer Chr'ss-l-wm H. mm

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FLAME-RETARDANT WIRE AND CABLE .This invention relates to electricalwire and cable and more particularly to electrical conducting wire andcable possessing relatively flameproof properties.

During the past several decades, the tray or ladder method of wiringindustrial plants has come more and more into widespread use. The traysystem involves the use of suspended metal work, in which wire and cableis laid in running the cable from a source of motive power to servicepanels or devices, as the case may be. This ladder or tray system is tobe contrasted with the system of pulling wires through specifieddiameter conduits which, of course, limits the size and number of cableswhich can eventually be connected from one place to another within afixed or prescribed conduit.

Tray systems are used in utility generating stations, steel mills andother industrial plants where the ease of running new cables in trays ina stacked fashion is common practice. The trays eventually end up instacked rows with layers of cable side-by-side to various heights. lnsuch plants, debris and foreign matter have a tendency to collect in thetrays and, if there is any fire hazard presented by other operationssuch as welding and the like, the trays with their multitudinous numberof cables set side-by-side and one upon another, pose aserious problemas to propagation of tire, smoke generation and the falling of burningparticles. Since the tray system is used in many utility and industrialinstallations, fires of electrical nature can result in severe damage toexpensive and critical equipment and devices and may propagatethroughout the entire plant via the tray route.

At present, the only electrical conductors or cables which, whensubjected to high temperatures of open flames, do not form burningfalling particles, propagate flame or generate smoke, are electricalconductors or cables which have coverings commonly made of metal, metalalloys or the like. These conductors or cables are relatively expensivebecause of the difficulty involved in producing the metal covering and,further, they are unwieldy, bulky and cumbersome and difficult andexpensive to repair and replace.

ln view of the foregoing, applicants have devised an electricalconductor or cable capable of maintaining electrical integrity forsustained periods of time beyond 5 minutes and up to as much as minuteswhen subjected to open flame temperatures in excess of l000 F. Theelectrical integrity will be maintained without producing any fallingburning particles which can deposit themselves on other devices ormaterials, causing separate and distinct fires from the original fire.In addition, the conductor or cable of this invention will not propagatea fire along its length when subjected to open flame conditions at aparticular source or region, nor will it generate large quantities ofsmoke.

Accordingly, it is a principal object of this invention to provide a newand improved flameproof electrical wire and cable.

Another object of this invention is to provide a new and improvedflameproof electrical wire and cable which will not produce falling,burning particles when subjected to open flame and which will notgenerate smoke.

Still another object of this invention is to provide a new and improvedflameproof electrical wire and cable which will not propagate a firealong its length when subjected to open flame at a particular point orregion.

A further object of this invention is to provide a new and improvedflameproof electrical wire and cable which will maintain electricalintegrity while subjected to an open flame, which electrical integritywill be maintained after the open flame hazard is removed.

A still further object of this invention is to provide a new andimproved flameproof electrical wire and cable which is substantiallyflexible and relatively inexpensive.

Still other objects and advantages of the invention will in part beobvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others and thearticle possessing the features, properties and the relation of elementswhich are exemplified in the following detailed disclosure and the scopeof the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following description, taken inconnection with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of the insulated wire of thisinvention;

FIG. 2 is an isometric exploded view of the insulated wire of FIG. 1;

H6. 3 is a cross-sectional view of an alternate embodiment of theinvention; and

FIG. 4 is a cross-sectional view of a cable insulated according to thisinvention.

In FIG. 1 there is illustrated a metal conductor 10 which may be ofstranded or solid metals, such as copper or copper coated tin, as thecase may be. Other metals, such as aluminum, silver plated copper, orother conductive alloys such as stainless steel, may also be utilized.The metal conductor may be a single solid metal conductor or a pluralityof metallic conductors. A layer of a primary insulation 11 is appliedover the conductor, generally in thicknesses of from about 5 mils to 2inches and, preferably, in thicknesses of from 10 mils to about one-halfinch.

In the preferred embodiment of the invention, the primary insulation llmay be Rockbestos X Link 90 (a blend of polyethylene and ethylenepropylene rubber which has been cross-linked) or other chemicallycross-linked polyethylene compounds, silicone rubber, heat-sealedpolyester tapes such as polyethylene terephthalates and ethylenepropylene rubber. Other insulating materials which may be used arepolyvinylchloride, polyethylene, nylon polysulfone, extruded polyester,butyl rubber, polytetrafluoroethylene and fluorinated ethylenepropylene. Moreover, it is to be understood that other, equivalentthermosetting materials may be used as primary insulation ll. Wheresuperior electrical properties are desired, silicone rubber ispreferable although the cost of silicone rubber is extremely high.Therefore, Rockbestos X Link 90 is preferred as the primary insulationsince it has good dielectric properties, does not readily melt uponexposure to very high temperatures and is relatively inexpensive lnapplying the insulation over the metallic conductor, the insulationlayer may be extruded or applied as a tape or film. In the preferredembodiment, an extruded layer of Rockbestos X Link 90 is applied,preferably in thicknesses of 10 mils to about 500 mils.

Immediately adjacent to the primary insulation layer 11, there is alayer of silicone rubber 12, generally in thicknesses of l mil to 10mils and, preferably, in thicknesses of 2 mils to 5 mils. The layer 12may be methyl silicone rubber, vinyl methyl silicone rubber, phenylsilicone rubber, fluoro silicone rubber, or other types of siliconerubber. Although methyl silicone rubber is preferred, it should beunderstood that any of the other silicone rubbers may be utilized. Thesilicone rubber may be applied to the primary insulation layer as a tapeor film or as part of a silicone rubber glass tape or film.

The layer of silicone rubber is a very effective insulation since, onexposure to high open flame temperatures, the layer reverts to anonconductive inert silica layer. This silica layer performs twofunctions: (1) it acts as a fireproof media and prevents oxygen frompassing through to the primary insulator and, thus, it prevents theprimary insulation from decomposing and losing its effectiveness, and(2) the silicone rubber layer does not lose its own effectiveness as aninsulation even though it is present as a silica layer.

Adjacent to and covering the silicone rubber layer 12, there is applieda glass fiber layer 13, generally in thicknesses of 3 mils to ID milsand, preferably, in thicknesses of 4 mils to 7 mils. Glass cloth, glassbraid or any other glass fiber such as glass mat, may be used to providethe required support and reinforcement for the silicone rubber layers.The glass cloth acts as an insulation and, as before, the glass clothmay be applied as a tape or film.

Directly over the glass fiber layer 13, there is applied another layerof silicone rubber 14, generally in thicknesses of 1 mil to mils and,preferably, in thicknesses of 2 mils to 5 mils. It should be understoodthat the second layer of silicone rubber is preferred, but is notnecessary to this invention. This second silicone rubber layer preventsoxygen from passing into the underlying layers. Thus, the combination oflayers l2, l3 and 14 provides a very effective insulation barrieragainst high open flame temperatures and prevents oxygen from passinginto and reacting with the primary insulation. The combination of thesilicone rubber layers 12, 14 and glass fiber layer 13 may take the formof a unitary layer, wherein the glass fiber has been coated orimpregnated on one or both sides with the silicone rubber.

Adjacent to and immediately over the silicone rubber layer 14 there isapplied a layer of asbestos 15, generally in thicknesses of 20 mils to90 mils and, preferably, in thicknesses of 25 mils to 50 mils,impregnated with an intumescent material. The asbestos layer 15 may bean asbestos braid or any loose asbestos fiber such as an asbestos felt.The asbestos provides mechanical protection for the wire or cable at allservice temperatures in wet or dry locations and is readily availableand inexpensive. In addition, asbestos has good bulk characteristics, inthat it readily absorbs intumescent material while glass and otherinorganic fibers are not very absorbent. Further, the asbestos has avery high melting point, is noncombustible and has the desirableproperty of expanding slightly at high temperatures. In actualoperation, the asbestos acts as a noncombustible, inorganichigh-strength support for the intumescent material at the elevated openflame temperatures to which it may be exposed. Moreover, the asbestoslayer serves the additional purpose of supporting the silicone rubberlayer 14 upon its reversion to silica when the system is exposed to anopen flame. The intumescent material in the asbestos, when subjected toopen flame temperatures, swells and forms a thermal insulatingfire-retardant barrier between the flame and the layers of insulatingmaterial underneath. As a result, the cable or wire does not propagate afire and there are no falling burning particles nor generation of densesmoke. Additionally, the flameproof electrical wire and cable of thepresent invention can be used in wet or dry locations. As a result, theelectrical conductor or cable of this invention need not have anadditional or ancillary protective coating such as metal braid, armor,conduit or tubing. Furthermore, a protective coating other than metalarmor would not have the fireproof characteristics of the intumescentimpregnated asbestos.

intumescent materials or compounds which may be used to impregnate orcoat the asbestos layer are raw isano oil, polyamide resins and aminefonnaldehyde resins. Examples of amine formaldehyde resins that havebeen found to be satisfactory in the present invention are melaminefonnaldehyde resin, urea formaldehyde resin and triazine fonnaldehyderesins. The polyamide resins used in the present invention are theproducts obtained by reacting a polymerized unsaturated vegetable acidwith an amine. For example, the polyamider esin may be obtained byreacting dimerized and trimerized linoleic acid or linoleic acid of soybean oil with ethylene diamide. It has been found that a superiorintumescent composition is obtained when a mixture of raw isano oil witha polyamide resin or an amine formaldehyde resin is prepared where theamount of raw isano oil is 33-70 percent of the total composition. Theuse of the above composition in intumescent paints is set forth in U.S.Pat. No. 2,754,217.

Other intumescent compounds which may be used as intumescent material toimpregnate the asbestos layer of the present invention are waterinsoluble metal metaphosphates, water insoluble polyols and waterinsoluble aminoplasts. Examples of water insoluble metal metaphosphatesare insoluble potassium metaphosphate, insoluble sodium metaphosphate,zinc" metaphosphate and calcium metaphosphate. Any of the waterinsoluble metaphosphate salts are applicable to this invention.

Various water insoluble polyhydric compounds may be used in variouspolymeric forms such as dimers or trimers, to impart intumescentproperties to the asbestos layer. In particular, polypentaerythritolssuch as dipentaerythritol and tripentaerythritol are preferred.

The aminoplasts or amino aldehyde condensation products are preparedfrom aldehydes and organic compounds containing at least one amino groupwhich has at least two replaceable hydrogens. The preferred compoundsare water insoluble urea formaldehyde condensation products. in general,the aminoplasts are prepared by reacting an aldehyde such asformaldehyde, urea aldehyde, propionaldehyde and the like with aminocompounds containing one to nine carbon atoms and having the grouping ofthe formula where N is a member selected from the group consisting of anitrogen atom having two single valences attached to separate atomsselected from the group consisting of hydrogen and carbon atoms, and anitrogen atom having two free valences representing a double bondattached to a carbon atom, and where Y is a member selected from thegroup consisting of O, S, and a nitrogen atom with one free valencewhich is attached to an atom selected from the group consisting ofhydrogen and carbon atoms.

in order to obtain superior intumescent properties, it is I preferred touse the above intumescent materials in combination in a compositioncontaining 27-66 percent by weight of polypentaerythritol with a waterinsoluble metal metaphosphate. Further, an aminoplast may be added tothe composition to increase the intumescent properties of thecomposition, such that the composition contains l5.70 percent by weightof urea formaldehyde resins. The uses of the above intumescentcompositions in paint is illustrated in U.S. Pat. No. 3,037,95 l.

Another compound suitable for use as an intumescent material, iswater-glass or sodium silicate. However, because of the solubility ofsodium silicate in water, this compound has limited utility as anintumescent compound to impregnate the asbestos according to thisinvention.

Other publications which describe the uses of intumescent materials inpaints, which intumescent materials or compositions are suitable for usein the present invention, are: J. Amer. Oil Chemists Soc.,Water-resistant, Oil-based, lntumescing Fire-retardant Coatings, 4l(10), 6704 (I964), and Off. Dig., .l. Paint Tech., Water-resistant,Oil-based, lntumescing Fire-retardant Coatings, 38 (793), l05-l2 (1966)(Eng).

The above intumescent compounds and compositions may be mixed ordissolved with a common carrier such as linseed oil, xylol, toluol andthe like, so that the resulting mixture may be applied to the asbestoslayer. lntumescent compositions premixed and suitable for theirapplication to the asbestos layer are sold under the tradenames of No.144639, Fire-retardant Coating, and Series 180, Coatings forCross-linked Polyethylenes, sold by the Standard T Chemical Company,Inc. The intumescent material may be added to the asbestos beforeorafter the asbestos has been placed on the silicone rubber layer 14,although it is preferred that the intumescent material be applied to theasbestos after the asbestos has been applied over the silicone rubberlayer. While it may be understood that the wire or cable dimensions ofthe present invention may vary according to the design for anyparticular application, the following is a typical range for theelectrical conducting system of the instant invention, applied in thegiven order:

(1)" Meta u1c conductors in wire-Typically tin-coated copper, inches 0.10-2 (2) Primary insultation on wire, mils 10-500 (3) First, layer ofsilicone rubber-Methyl silicone rubber, mils 2-5 (4) Glass cloth layer,mils 4-7 (5) Second layer of silicone rubber-Methyl silicone rubber,mils 2-5 (6) Asbestos braid la verContaining intumescent material, mils25-50 It is to be understood that the above dimensions are typical andnot intended to limit the invention in any way.

A wire of the present invention was subjected to the flame of a bunsenburner (in excess of 1500" F. for 10 minutes. The exposed wire was foundto have substantial insulation left and was capable of passing thedielectric test. Thus, electric integrity was maintained, there were nofalling, burning particles and fire was not propagated along the wirenor was excessive smoke generated.

An alternate embodiment of the invention is illustrated in FIG. 3.Insulation layers 11-14 are the same as those disclosed with referenceto FIGS. 1 and 2. As in the embodiment of FIG. 1, the second siliconerubber layer 14 may or may not be present. In the preferred form of thealternate embodiment, there is utilized a second silicone rubber layer.Silicone rubber layer 1.4 is covered by a layer of asbestos tape 16 orother form of asbestos wherein the fibers are closely woven. Sinceasbestos tape is rather closely woven, it is difficult to properlyimpregnate with intumescent material. Therefore, in place of theintumescent material, asbestos tape layer 16 is covered by a layer of anelastomeric material 17 having suitable fireproofing properties. Theelastomeric material may be any elastomeric material to which thenecessary fire-retardant compounds may be added and which can beextruded about asbestos tape layer 16. Some examples of such elastomersare butyl rubber, silicone rubber, polyurethene rubber, neoprene,butadiene acrylonitrile, chlorosulfonated polyethylene and butadienestyrene. Before the elastomeric material is extruded over the asbestos,chlorinated parafins and halogenated phenols are compounded into it toimpart additional fire-retardant properties to the material. Someexamples of chlorinated parafins which were found suitable for thepresent invention are Chlorofin (trademark) manufactured by HerculesChemical Company, Halowax (trademark) manufac' tured by The UnionCarbide Corporation, and Chlorowax (trademark) manufactured by TheDiamond Alkali Company. Halogenated phenols which were found suitablefor imparting fire-retardant properties to the elastomeric material aretetrabromobisphenol, hexachlorophene and dichlorophene. Although, in thepreferred embodiment, both chlorinated 'parafins and halogenated phenolsare compounded into the elastomeric material, it should be understoodthat only one of the above two classes of compounds need be added.Further, to impart additional fire-retardant properties to theelastomeric material, fire-retardant inorganic compounds such asphosphates and borates, can be compounded into it. Specifically,compounds which were found to produce excellent results are antimonytrioxide, zinc borate, tricresylphosphate, trioctylphos'phate andtriphenylphosphate. In particular, the interaction between antimonytrioxide and chlorinated material to produce the intermediate, antimonyoxychloride, at elevated temperatures, has proven an efl'rcacious flameretardant. ln'the preferred embodiment, all threeclasses of compoundswere compounded into the elastomeric material so as to impart to itmaximum fire-retardant properties.

Layer 17 is generally 0.045 to 0.140-inches thick and, preferably, 0.060to 0.140-inches thick. Since the combination of the glass fiber,asbestos tape. and elastomeric material forms a layer which is highlyimpermeable to gases, this type of insulation presents a problem whenthe insulated wire or cable is exposed to fires. Thus, gases that areformed in the lower layers of insulation are trapped by the outer layersof glass fiber, asbestos tape and elastomeric material so that, as aresult of increasing pressure of the trapped gases, the insulation comesapart. This problem is resolved in the present invention by having thelay of the layer of glass fiber and the asbestos tapelayer in the samedirection, to form a loose combination of layers. With respect tocables, the lay of the wires, the glass fiber layer and the asbestostape layer are all in the same direction. The loose layers, that is, thelayers of insulation having their lay in the same direction, expandunder the influence of the pressure of the trapped gases allowing thetrapped gases to pass, or travel, beneath the insulation and parallel tothe axis of the wire or cable. This prevents the insulation from beingtorn apart.

Although such a loose covering of insulation is not usually desirable,it is used in a case where it is preferred to use an insulation systemhaving the two external layers of asbestos tape and elastomeric materialinstead'of asbestos it should'be noted that the insulation system ofthis embodiment has fireproofing properties which are even better thanthose of the insulation system wherein intumescent material is used.

The basic insulation system of the present invention comprises a layerof primary insulation which is then covered by a layer of glass fiber.The glass fiber layer has at least one layer of silicone rubber on oneof its sides. Preferably, both sides of the glass fiber layer arecovered with silicone rubber. The layer of silicone rubber is, at thispoint, covered by a layer of asbestos. This is the basic insulationsystem of the present invention, which has the exceptional fireproofingproperties described above. In addition, if an external layer ofasbestos braid or asbestos felt, or any other loosely-packed asbestosfiber material is used, then the asbestos material can be impregnatedwith intumescent material to impart to the insulation additionalfireproofing properties. On the other hand, if an external layer ofasbestos tape is used, then an outer layer of elastomeric material,having suitable fire-retardant properties, is used to cover the asbestostape. In this embodiment, the lay of the glass fiber layer and theasbestos tape layer is in the same direction so as to form a loosecovering over the conductor.

In FIG. 4, there is illustrated a cable insulated according to thepresent invention. A plurality of individual metal conductors 18,wherein each conductor may be composed of stranded or solid metals suchas copper or copper coated with tin, as the case may be, are showncovered by a layer of prima- 'ry insulation 19, generally 5-500 mils inthickness and, preferably, in a thickness of from l0250 mils. Theprimary insulation 19 is selected from the same class of material asprimary insulation ll. Covering the primary insulation 19 on theinsulated wires 18, there may or may not be a layer of intermediatecovering material 20. The intermediate covering material 20 may beneoprene, polyvinylchloride or any other thermosetting or thermoplasticinsulation, which may be applied by extrusion or any other suitablemanner. Generally, the layer of intermediate covering material is of 30-I00 mils thickness and, preferably, is of 4080 mils thickness. To theintermediate covering material 20 there is applied a covering of a layerof silicone rubber 21, generally in a thickness of l- 10 mils and,preferably, in a thickness of 2-5 mils.

Immediately adjacent and above the silicone rubber layer, there isapplied a glass fiber layer 22, generally of 3-10 mils thickness and,preferably, 4-7-mils thick. The glass fiber layer 22 is subsequentlycovered by a layer of silicone rubber 23, again in a thickness ofgenerally 1 to 10 mils and, preferably of 25 mils. As explained withreference to FIGS. l3, the second silicone rubber layer 23 may or maynot be present. However, a second silicone rubber layer impartsadditional fireproofing properties. Then, as in the embodimentillustrated in FIGS. 1 and 2, the second layer of siliconerubber 23 iscovered by a layer of asbestos braid 24, impregnated with intumescentmaterial of a thickness of generally 20-90 mils and, preferably, 25 to50 mils. The primary insulation layer 19, the silicone rubber layers 21,23, the glass fiber layer '22, and, the impregnated asbestos layer 24,are as described with reference to FIGS. 1 and 2.

With respect to cables, as in the-case of a single electrical conductor,when the asbestos used to cover the second layer of silicone rubbercomprises asbestos braid or any other asbestos material composed ofloose fibers, the asbestos is impregnated with intumescent material.However, when the external asbestos layer is composed of asbestos tapeor any other closely woven asbestos material, the asbestos is coveredwith a layer of elastomeric material having good fireproofingproperties,as has been explained previously in connection with FIG.

" 3. As in the case of single electrical conductors, the elastomericlayer coveringthe asbestos tape is generally 0.025 to 0.200-

' inches thick and, preferably, 0.050 to 0.100-inches thick.

above article without departing from the spirit and scope of theinvention, it is intended that all matter contained in the abovedescription and shown in the accompanying drawing shall be interpretedas illustrative and not in a limiting sense.

It is also to be understood that thefollowing claims are intended tocover all the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween. We claim:

1. An electrical insulated conductor, capable of maintaining electricalintegrity when exposed to open flame temperatures of at least 1000 F.without propagating a fire or resulting in falling burning particles orgenerating dense smoke, comprising:

a. a metallic conductor,

b. a layer of primary insulation which covers said metallic conductoralong its length, c. a layer of glass fiber over the layer of primaryinsulation, d. a layer of silicone rubber on one side of said layer ofglass fiber; and e. a layer of asbestos which covers said layers ofglass fiber and silicone rubber, said asbestos fibers impregnated withan intumescent material said layer of asbestos being the 1 outer layerof said insulated conductor.

2. The electrical conductor of claim 1, wherein the lay of the layers ofglass fiber and asbestos is in the same direction.

3. The electrical conductor of claim 1, wherein the electriv calconductor is selected from the group consisting of a single solidconductor and a plurality of solid conductors.

4. The electrical conductor of claim 1, wherein the glass fiber layer iscovered on both sides with a layer of silicone rubber.

5.,The electrical conductor of claim 1, wherein the primary insulationis selected from the class of compounds consisting of chemicallycross-linked polyethylene compounds, silicone rubbers, heat-sealedpolyester tapes such as polyethylene v terephthalate, ethylene propylenerubber, nylon, butylrubber,

polysulfone, polyvinylchloride, polytetrafiuoroethylene and fluorinatedethylene propylene.

6. The electrical conductor of claim 1, wherein the intumescent materialis selected from the class consisting of raw isano oil, polyamideresins, amine formaldehyderesins, water insoluble metal metaphosphates,polypentaerythritols, sodium silicate andcombinations thereof.

1 7. The electrical conductor of claim 1, wherein the glass fiber isselected from the group consisting of glass cloth, glass braid, glassmat and other glass fibers and combinations thereof.

8. An electrical insulated cable, capable of maintaining electricalintegrity when exposed to open flame temperatures of at least l000 F.without propagatinga fire or resulting in falling burning particles orgenerating dense smoke, comprismg: i

a. a plurality of metallic conductors, I b. a layer of primaryinsulation which covers and separates the plurality of metallicconductors along their lengths such that each metallic conductor isinsulated from the other conductors, c. a layer of glass fiber over saidprimary insulation, d. a layer of silicone rubber on one side of saidlayer of glass fiber; and b e. a layer of asbestos which covers saidlayers of glass fiber and silicone rubber. 9. The electrical cable ofclaim 8, wherein the layer of asbestos comprises asbestos selected fromthe group consisting of asbestos braid, asbestos mat and asbestos felt,which asbestos material is impregnated with an intumescent material.

10. The electrical cable of claim 8, wherein the layer of asbestoscomprises asbestos tape which is then covered by a layer of anelastomeric material selected from the group consisting of neoprene,butadiene acrylonitrile, chlorosulfonated polyethylene and butadienestyrene.

11. The electrical insulated cable of claim 8, wherein a layer ofsilicone rubber covers both sides of said layer of glass fiber.

12. The electrical insulated cable of claim 8, further includ' ing anintermediate layer of insulating material which covers the plurality ofmetallic conductors insulated with the primary insulation and isimmediately beneath the layer of glass fiber, wherein said material isselected from the group consisting of neoprene and polyvinylchloride.

13. The electrical cable of claim 10, wherein the lay of the wires, theglass fiber layer and the asbestos tape layer is in the same direction.

14. The electrical cable of claim 8, wherein the primary insulation isselected from the class of compounds consisting of chemicallycrosslinked polyethylene compounds, silicone rubber, heat-sealedpolyester tapes such as polyethylene terephthalate, ethylene propylenerubber, nylon, butyl rubber, polysulfane, polyvinylchloride,polytetrafluoroethylene and fluorinated ethylene propylene.

15. The electrical cable of claim 9, wherein the intumescent material isselected from the class consisting of raw isano oil, polyamide resins,amine formaldehyde resins, water insoluble metal metaphosphates,polypentaerythritols, sodium silicate and combinations thereof.

16. The electrical cable of claim 8, wherein the glass fiber is selectedfrom the class consisting of glass cloth, glass braid, glass mat andother glass fibers and combinations thereof.

17. The electrical conductor of claim 10, wherein the elastomericmaterial has compounded therein a chlorinated parafin.

18. The electrical conductor of claim 10, wherein the elastomericmaterial has additionally compounded therein halogenated phenolsselected from the group consisting of tetrabromobisphenol,hexachlorophene and dichlorophene.

19. The electrical conductor of claim 10, wherein the elastomericmaterial has additionally compounded therein fire-retardant inorganiccompounds selected from the group consisting of antimony trioxide, zincborate, tricresylphosphate, trioctylphosphate and triphenylphosphate.

2. The electrical conductor of claim 1, wherein the lay of the layers ofglass fiber and asbestos is in the same direction.
 3. The electricalconductor of claim 1, wherein the electrical conductor is selected fromthe group consisting of a single solid conductor and a plurality ofsolid conductors.
 4. The electrical conductor of claim 1, wherein theglass fiber layer is covered on both sides with a layer of siliconerubber.
 5. The electrical conductor of claim 1, wherein the primaryinsulation is selected from the class of compounds consisting ofchemically cross-linked polyethylene compounds, silicone rubbers,heat-sealed polyester tapes such as polyethylene terephthalate, ethylenepropylene rubber, nylon, butyl rubber, polysulfone, polyvinylchloride,polytetrafluoroethylene and fluorinated ethylene propylene.
 6. Theelectrical conductor of claim 1, wherein the intumescent material isselected from the class consisting of raw isano oil, polyamide resins,amine formaldehyde resins, water insoluble metal metaphosphates,polypentaerythritols, sodium silicate and combinations thereof.
 7. Theelectrical conductor of claim 1, wherein the glass fiber is selectedfrom the group consisting of glass cloth, glass braid, glass mat andother glass fibers and combinations thereof.
 8. An electrical insulatedcable, capable of maintaining electrical integrity when exposed to openflame temperatures of at least 1000* F. without propagating a fire orresulting in falling burning particles or generating dense smoke,comprising: a. a plurality of metallic conductors, b. a layer of primaryinsulation which covers and separates the plurality of metallicconductors along their lengths such that each metallic conductor isinsulated from the other conductors, c. a layer of glass fiber over saidprimary insulation, d. a layer of silicone rubber on one side of saidlayer of glass fiber; and e. a layer of asbestos which covers saidlayers of glass fiber and silicone rubber.
 9. The electrical cable ofclaim 8, wherein the layer of asbestos comprises asbestos selected fromthe group consisting of asbestos braid, asbestos mat and asbestos felt,which asbestos material is impregnated with an intumescent material. 10.The electrical cable of claim 8, wherein the layer of asbestos comprisesasbestos tape which is then covered by a layer of an elastomericmaterial selected from the group consisting of neoprene, butadieneacrylonitrile, chlorosulfonated polyethylene and butadiene styrene. 11.The electrical insulated cable of claim 8, wherein a layer of siliconerubber covers both sides of said layer of glass fiber.
 12. Theelectrical insulated cable of claim 8, further including an intermediatelayer of insulating material which covers the plurality of metallicconductors insulated with the primary insulation and is immediatelybeneath the layer of glass fiber, wherein said material is selected fromthe group consisting of neoprene and polyvinylchloride.
 13. Theelectrical cable of claim 10, wherein the lay of the wires, the glassfiber layer and the asbestos tape layer is in the same direction. 14.The electrical cable of claim 8, wherein the primary insulation isselected from the class of compounds Consisting of chemicallycross-linked polyethylene compounds, silicone rubber, heat-sealedpolyester tapes such as polyethylene terephthalate, ethylene propylenerubber, nylon, butyl rubber, polysulfane, polyvinylchloride,polytetrafluoroethylene and fluorinated ethylene propylene.
 15. Theelectrical cable of claim 9, wherein the intumescent material isselected from the class consisting of raw isano oil, polyamide resins,amine formaldehyde resins, water insoluble metal metaphosphates,polypentaerythritols, sodium silicate and combinations thereof.
 16. Theelectrical cable of claim 8, wherein the glass fiber is selected fromthe class consisting of glass cloth, glass braid, glass mat and otherglass fibers and combinations thereof.
 17. The electrical conductor ofclaim 10, wherein the elastomeric material has compounded therein achlorinated parafin.
 18. The electrical conductor of claim 10, whereinthe elastomeric material has additionally compounded therein halogenatedphenols selected from the group consisting of tetrabromobisphenol,hexachlorophene and dichlorophene.
 19. The electrical conductor of claim10, wherein the elastomeric material has additionally compounded thereinfire-retardant inorganic compounds selected from the group consisting ofantimony trioxide, zinc borate, tricresylphosphate, trioctylphosphateand triphenylphosphate.